B\u00e0i t\u1eadp tr\u1eafc nghi\u1ec7m H\u00ecnh h\u1ecdc 12 \u2013 Ch\u01b0\u01a1ng 1 – B\u00e0i 2: Kh\u1ed1i \u0111a di\u1ec7n l\u1ed3i v\u00e0 kh\u1ed1i \u0111a di\u1ec7n \u0111\u1ec1u (Ph\u1ea7n 1)<\/a><\/blockquote><\/iframe>